The role of cover and rebar characteristics on load-slip behavior of reinforced concrete members in compression

Abstract

This paper describes a part of an extensive research work devoted to evaluate the bond strength between rebars and concrete through different testing procedures. Main parameters in this part are the concrete cover and rebar diameter. The tested specimen consisted of a single bar embedded in a concrete block with square cross-sectional area and is being tested under compressive load. Three concrete block sizes were cast to offer three different cover for the embedded rebars. The dimensions of these blocks were; 150×150×135, 100×100×135 and 200×200×185 mm. Three bar diameters, 12, 16 and 20 mm, were investigated. The specimens were water-cured and tested at the ages of 7 and 28 days. A new proposed test set-up was used to monitor the load-slip behavior of the specimens. The test results showed that there is no significant difference in bond energy between the two curing ages, 7 and 28 days. The concrete cover has a significant effect on the bond strength between rebar and concrete. By increasing the cover, the confinement offered by concrete increases, bond strength increases, and slip increases. Based on the present results, a concept of effective cover was developed. This concept showed a high correlation with the mode of failure for the tested specimens.